Well, you can use Compiz with KDE, for one thing. But since KDE 4 has a compositing window manager I prefer to use that, since window manager-wise KWin is a better, more solid window manager. (Compiz has better effects... for now )

But the real strength of KDE lies with its apps and configurability. I just like them better than Gnome's. KDE's apps have lots of great features, and the artwork is sexy. Qt4 and Oxygen help with this a lot.

Why KDE? Because I have yet to find something that gnome can while KDE can't. Plus, it looks better(after a bit of configuring), is far more configurable(my systems look far from default), is faster, uses less memory, has network-transparency, konqueror can embed just about anything, and a whole range of other more minor things.
The only thing gnome does better is that it has less cluttering, and the default style is somewhat prettier. I can live with the cluttering, and the default style doesn't survive long with me anyways...
I'm now using KDE4 svn, rebuilt about weekly(easy on gentoo), on my pc and KDE3.5 with some 4.0.2 on my laptop. KDE4 averall already is an improvement, and improving continously, but still has some annoyances to get rid of, and is still missing some things 3 had.

I don't know if it's just GTK or if it's GNOME as a whole. But quite a few things seem completely braindead to me. Like I mentioned, the file dialog of course sucks big time. Another thing was with fonts. I started out with Xfce and GTK programs, and I have wondered for an extremely long time why japanese fonts were so unbelievably ugly, with no anti-aliasing applied no matter what I did. Since I still don't have an alternative for emesene and Firefox, wich is where I would see the fonts the most, I didn't notice until a while ago that, in Qt/KDE programs they are fine! They are completely smooth. But whenever I see japanese text in GTK programs they are very ugly. There also seems to be annoying problems with fullscreen with window managers that are based on GTK. Another problem with GTK is that if you open any folder that has many files, it takes a lot of time to load up. With Qt, the same folder comes up instantly.

Because of these issues, wich I am sure the devs have no interest in fixing (wich btw are only the ones I can remember right now, there are probably more issues), I am very glad that KDE uses Qt. I also like that KDE is very configurable. You can basically change just about anything you want in KDE through graphical menus, where you would need hackish solutions or extra programs for GNOME. There is also the speed. KDE includes a lot really, but yet it is fast, I saw benchmarks where it consumes less RAM than Xfce, and Xfce is a minimalist desktop. (Probably GTK's fault again) And that was compared with KDE 3.5x, KDE4 (apart from where bugs make it slow) is much faster than 3.5x.

I also like that KDE is for integration. In my KDE settings menus I can change things for both GTK programs and WINE. I think the KDE devs also tried to make drag-and-drop work between GTK and Qt apps, and also tried to decide on icon names together with GNOME (so that both can use the same icons), but afaik GNOME was not interested in helping with this.

You can probably see my hatred for GTK and GNOME here. I am usually quite calm, but lately I have gotten extremely tired with the 3 evils in GNU/Linux (GTK, GNOME and ALSA).

Oh, and this is sort of a shameless plug for Diggs so, OMG DIGG PLZZZ!!!!11!!1one!11!1!

Couldnt you just PM me the story, lol.
I myself really got pretty tired of all the GTK and Gnome mentality. These are truly turning into liabilities. Rarely I've seen software regress rather than progress, and have such shameful changelogs. If only kubuntu was a firstclass citizen for Canonical......

Kubuntu 8.10 Intrepid Ibex will feature KDE 4.1 as default. I will be upgrading to Intrepid early once it gets any form of KDE 4.1 pre-release packages, be it 4.1 Beta1 or Beta2 or whatever. (No way am I waiting until October for Intrepid, KDE 4.1 will already be 3 months old by then...)